Brush



Jan. 5 926. 1,568,774

T. J. SCOFIELD BRUSH Filed May 17 1923 I/vvnvrm Patented Jan. 5, 1926.

UNITED STATES PATENT OFFICE.

THEODORE J'. SCOFIELD, OF JACKSON, MICHIGAN, ASSIGNOR TO THE SPARKS-WITH- INGTON COMPANY, OF JACKSON, MICHIGAN, A CORPORATION OF OHIO.

BRUSH.

Application filed May 17, 1923. Serial No. 639,838.

To all whom it may concern:

Be it known that I, THEODORE J. SCOFIELD, a citizen of the United States, residing at Jackson, in the county of Jackson, in the State of Michigan, have invented new and useful Improvements in Brushes, of which the following, taken in connection with the accompanying drawings, is a full, clear, and exact description.

This invention relates to brushes used for carrying electric current to or from a moving contact and to or from a stationary contact, and pertains particularly to commutator brushes for use in connection with motors, dynamos or other electrical apparatus.

The main object of the invention is to lubricate the commutator surfaces without adding resistance to the How of current between the holder and the brush or between the brush and the commutator, and without otherwise effecting the efficiency of the brush. Numerous attempts have been made to produce eflicient: brushes and numerous characters of brushes are known, but for low voltages there has never been a brush that formed a sliding contact in connection with which there was assmall a voltage drop as there is with the known gauze brush,

but this known gauze brush has always had a tendency to cut the contact surfaces and cause undue wear.

Further, there have been attempts made to prevent the cutting of the contact surfaces and to prevent undue wear by impregnating the gauze with different materials, such.as graphite, carbon and different alloys.

On many electrical devices, it is impracn-tical and almost impossible to prevent oil getting onto these surfaces, and in the case of brushes filled with graphite or carbon, there is thus produced a paste-like substance which ruins the commutation and in the case of the brush completely impregnated with an alloy, there is a resistanceto the passage of current between the brush and the brush-holder which increases with use until the device is rendered in brush is that it binds the gauze and makes the greatest advantages of the gauze brush which resides in the flexibility of the brush, permitting it to seat readily on the surface with which it is to contact, and further requires accurate fitting of the brush or time to allow it to wear to a fit before the brush has contact surface enough to carry the required amount of electricity.

The brush of this invention is designed with the idea of retaining all of the ad vantages of the gauze brush, including the lubricating feature, without obtaining any of the undesirable features heretofore encountered.

][n the drawings t Figure 1 is a perspective View of a brush of my invention.

and no further description of the particular construction or formation of such a brush is required.

The brush so formed is preferably as shown of substantially square cross-section, altho obviously the shape of the brush may be widely varied. The front or contact face of the brush is formed concave'so as to fit a commutator of predetermined radius.

The brush so formed is partially 'impregnated with solder or amixture of lead and tin in any suitable manner, as for instance, by dipping the forward end into an alloy with the brush held at an angle so as to impregnate a substantially triangular portion of the brush with the alloy. Preferably, as shown, this triangular portion -2- constitutes substantially one-half of the surface area of the concave end 3- of the brush and extends diagonally of the brush to one side thereof.

It will be noted that the impregnated portion 2 constitutes a comparatively small portion oft-he brush 1, altho it extends over substantially one-half the area of the concave face 3 so as to leave the remaining portion of the concave face 3-- for direct and intimate contact with the commutator surface. The impregnated portion -2 should be arranged in such manner so as toconstitute the toe of the brush when assembled for operation.

It will be noted that with this construction the necessary lubricant is supplied to the commutator surfaces without in any way interfering with the flexibility or electrical efliciency of the brush.

Obviously the particular form and size of the impregnated portion of the brush as here illustrated is merely preferable as various changes may be made, in the method of pregnated portion so long as only a portion of the brush is impregnated, such portion constituting a'substantial part of the concave contact surface of the brush, but at the same time leaving also a substantial portion of said concave surface unimpregnated for intimate contact relation with the commutator surface.

I claim:

1. A commutator brush consisting of wire gauze material and having a concave contact surface at its front end, a portion of said brush being impregnated with a lubricating metallic alloy, such impregnated ortion constituting the complete width of t e contact surface of the brush when in use, approximately one-half of the area of said contact surface and a portion only of the length of the brush.

2. A wire brush having a concave contact surface, a substantially trian ular portion of said brush impre nated wit a metallic alloy, such trianguIar portion having one of its sides constituting a portion of said concave surface.

3. A gauze brush having a concave end impregnated with a metallic alloy, one of the sides of said prism constituting a portion only of the contact surface of said brush.

In witness whereof I have hereunto set my hand this 4th day of May, 1923.

THEODORE J. SQOFIELD. 

